Diatoms represent one of the largest groups of Stramenopiles. In the phytoplankton biodiversity, they dominate oceanic and freshwater ecosystems, and contribute significantly to biogeochemical cycles. They are primary producers at the base of food webs, capturing dissolved CO2, inorganic nitrogen, phosphorus, sulfur, etc., and are important carriers of carbon and silicon to the ocean interior. Whereas extensive studies of P. tricornutum response to a lack of nitrogen have been reported from transcriptomics to metabolomics and lipidomics, changes occurring at the proteome level are still missing. Here we aimed at providing a reference dataset, corresponding to the proteomic changes occurring when Phaeodactylum tricornutum cells were cultivated in either a nitrogen-rich or a nitrogen-poor medium.